# Functions for Working with H3 Indexes

## H3 Index​

H3 is a geographical indexing system where Earth’s surface divided into a grid of even hexagonal cells. This system is hierarchical, i. e. each hexagon on the top level ("parent") can be split into seven even but smaller ones ("children"), and so on.

The level of the hierarchy is called resolution and can receive a value from 0 till 15, where 0 is the base level with the largest and coarsest cells.

A latitude and longitude pair can be transformed to a 64-bit H3 index, identifying a grid cell.

The H3 index is used primarily for bucketing locations and other geospatial manipulations.

The full description of the H3 system is available at the Uber Engineering site.

## h3IsValid​

Verifies whether the number is a valid H3 index.

Syntax

h3IsValid(h3index)

Parameter

• h3index — Hexagon index number. UInt64.

Returned values

• 1 — The number is a valid H3 index. UInt8.
• 0 — The number is not a valid H3 index. UInt8.

Example

Query:

SELECT h3IsValid(630814730351855103) AS h3IsValid;

Result:

┌─h3IsValid─┐│         1 │└───────────┘

## h3GetResolution​

Defines the resolution of the given H3 index.

Syntax

h3GetResolution(h3index)

Parameter

• h3index — Hexagon index number. UInt64.

Returned values

• Index resolution. Range: [0, 15]. UInt8.
• If the index is not valid, the function returns a random value. Use h3IsValid to verify the index. UInt8.

Example

Query:

SELECT h3GetResolution(639821929606596015) AS resolution;

Result:

┌─resolution─┐│         14 │└────────────┘

## h3EdgeAngle​

Calculates the average length of the H3 hexagon edge in grades.

Syntax

h3EdgeAngle(resolution)

Parameter

• resolution — Index resolution. UInt8. Range: [0, 15].

Returned values

• The average length of the H3 hexagon edge in grades. Float64.

Example

Query:

SELECT h3EdgeAngle(10) AS edgeAngle;

Result:

┌───────h3EdgeAngle(10)─┐│ 0.0005927224846720883 │└───────────────────────┘

## h3EdgeLengthM​

Calculates the average length of the H3 hexagon edge in meters.

Syntax

h3EdgeLengthM(resolution)

Parameter

• resolution — Index resolution. UInt8. Range: [0, 15].

Returned values

• The average length of the H3 hexagon edge in meters. Float64.

Example

Query:

SELECT h3EdgeLengthM(15) AS edgeLengthM;

Result:

┌─edgeLengthM─┐│ 0.509713273 │└─────────────┘

## h3EdgeLengthKm​

Calculates the average length of the H3 hexagon edge in kilometers.

Syntax

h3EdgeLengthKm(resolution)

Parameter

• resolution — Index resolution. UInt8. Range: [0, 15].

Returned values

• The average length of the H3 hexagon edge in kilometers. Float64.

Example

Query:

SELECT h3EdgeLengthKm(15) AS edgeLengthKm;

Result:

┌─edgeLengthKm─┐│  0.000509713 │└──────────────┘

## geoToH3​

Returns H3 point index (lon, lat) with specified resolution.

Syntax

geoToH3(lon, lat, resolution)

Arguments

• lon — Longitude. Float64.
• lat — Latitude. Float64.
• resolution — Index resolution. Range: [0, 15]. UInt8.

Returned values

Example

Query:

SELECT geoToH3(37.79506683, 55.71290588, 15) AS h3Index;

Result:

┌────────────h3Index─┐│ 644325524701193974 │└────────────────────┘

## h3ToGeo​

Returns the centroid longitude and latitude corresponding to the provided H3 index.

Syntax

h3ToGeo(h3Index)

Arguments

• h3Index — H3 Index. UInt64.

Returned values

• A tuple consisting of two values: tuple(lon,lat). lon — Longitude. Float64. lat — Latitude. Float64.

Example

Query:

SELECT h3ToGeo(644325524701193974) AS coordinates;

Result:

┌─coordinates───────────────────────────┐│ (37.79506616830252,55.71290243145668) │└───────────────────────────────────────┘

## h3ToGeoBoundary​

Returns array of pairs (lon, lat), which corresponds to the boundary of the provided H3 index.

Syntax

h3ToGeoBoundary(h3Index)

Arguments

• h3Index — H3 Index. UInt64.

Returned values

Example

Query:

SELECT h3ToGeoBoundary(644325524701193974) AS coordinates;

Result:

┌─h3ToGeoBoundary(599686042433355775)────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐│ [(37.2713558667319,-121.91508032705622),(37.353926450852256,-121.8622232890249),(37.42834118609435,-121.92354999630156),(37.42012867767779,-122.03773496427027),(37.33755608435299,-122.090428929044),(37.26319797461824,-122.02910130919001)] │└────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘

## h3kRing​

Lists all the H3 hexagons in the raduis of k from the given hexagon in random order.

Syntax

h3kRing(h3index, k)

Arguments

• h3index — Hexagon index number. UInt64.
• k — Radius. integer

Returned values

Example

Query:

SELECT arrayJoin(h3kRing(644325529233966508, 1)) AS h3index;

Result:

┌────────────h3index─┐│ 644325529233966508 ││ 644325529233966497 ││ 644325529233966510 ││ 644325529233966504 ││ 644325529233966509 ││ 644325529233966355 ││ 644325529233966354 │└────────────────────┘

## h3GetBaseCell​

Returns the base cell number of the H3 index.

Syntax

h3GetBaseCell(index)

Parameter

• index — Hexagon index number. UInt64.

Returned value

• Hexagon base cell number. UInt8.

Example

Query:

SELECT h3GetBaseCell(612916788725809151) AS basecell;

Result:

┌─basecell─┐│       12 │└──────────┘

## h3HexAreaM2​

Returns average hexagon area in square meters at the given resolution.

Syntax

h3HexAreaM2(resolution)

Parameter

• resolution — Index resolution. Range: [0, 15]. UInt8.

Returned value

Example

Query:

SELECT h3HexAreaM2(13) AS area;

Result:

┌─area─┐│ 43.9 │└──────┘

## h3HexAreaKm2​

Returns average hexagon area in square kilometers at the given resolution.

Syntax

h3HexAreaKm2(resolution)

Parameter

• resolution — Index resolution. Range: [0, 15]. UInt8.

Returned value

• Area in square kilometers. Float64.

Example

Query:

SELECT h3HexAreaKm2(13) AS area;

Result:

┌──────area─┐│ 0.0000439 │└───────────┘

## h3IndexesAreNeighbors​

Returns whether or not the provided H3 indexes are neighbors.

Syntax

h3IndexesAreNeighbors(index1, index2)

Arguments

• index1 — Hexagon index number. UInt64.
• index2 — Hexagon index number. UInt64.

Returned value

• 1 — Indexes are neighbours. UInt8.
• 0 — Indexes are not neighbours. UInt8.

Example

Query:

SELECT h3IndexesAreNeighbors(617420388351344639, 617420388352655359) AS n;

Result:

┌─n─┐│ 1 │└───┘

## h3ToChildren​

Returns an array of child indexes for the given H3 index.

Syntax

h3ToChildren(index, resolution)

Arguments

• index — Hexagon index number. UInt64.
• resolution — Index resolution. Range: [0, 15]. UInt8.

Returned values

Example

Query:

SELECT h3ToChildren(599405990164561919, 6) AS children;

Result:

┌─children───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐│ [603909588852408319,603909588986626047,603909589120843775,603909589255061503,603909589389279231,603909589523496959,603909589657714687] │└────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘

## h3ToParent​

Returns the parent (coarser) index containing the given H3 index.

Syntax

h3ToParent(index, resolution)

Arguments

• index — Hexagon index number. UInt64.
• resolution — Index resolution. Range: [0, 15]. UInt8.

Returned value

Example

Query:

SELECT h3ToParent(599405990164561919, 3) AS parent;

Result:

┌─────────────parent─┐│ 590398848891879423 │└────────────────────┘

## h3ToString​

Converts the H3Index representation of the index to the string representation.

h3ToString(index)

Parameter

• index — Hexagon index number. UInt64.

Returned value

• String representation of the H3 index. String.

Example

Query:

SELECT h3ToString(617420388352917503) AS h3_string;

Result:

┌─h3_string───────┐│ 89184926cdbffff │└─────────────────┘

## stringToH3​

Converts the string representation to the H3Index (UInt64) representation.

Syntax

stringToH3(index_str)

Parameter

• index_str — String representation of the H3 index. String.

Returned value

• Hexagon index number. Returns 0 on error. UInt64.

Example

Query:

SELECT stringToH3('89184926cc3ffff') AS index;

Result:

┌──────────────index─┐│ 617420388351344639 │└────────────────────┘

## h3GetResolution​

Returns the resolution of the H3 index.

Syntax

h3GetResolution(index)

Parameter

• index — Hexagon index number. UInt64.

Returned value

• Index resolution. Range: [0, 15]. UInt8.

Example

Query:

SELECT h3GetResolution(617420388352917503) AS res;

Result:

┌─res─┐│   9 │└─────┘

## h3IsResClassIII​

Returns whether H3 index has a resolution with Class III orientation.

Syntax

h3IsResClassIII(index)

Parameter

• index — Hexagon index number. UInt64.

Returned value

• 1 — Index has a resolution with Class III orientation. UInt8.
• 0 — Index doesn't have a resolution with Class III orientation. UInt8.

Example

Query:

SELECT h3IsResClassIII(617420388352917503) AS res;

Result:

┌─res─┐│   1 │└─────┘

## h3IsPentagon​

Returns whether this H3 index represents a pentagonal cell.

Syntax

h3IsPentagon(index)

Parameter

• index — Hexagon index number. UInt64.

Returned value

• 1 — Index represents a pentagonal cell. UInt8.
• 0 — Index doesn't represent a pentagonal cell. UInt8.

Example

Query:

SELECT h3IsPentagon(644721767722457330) AS pentagon;

Result:

┌─pentagon─┐│        0 │└──────────┘

## h3GetFaces​

Returns icosahedron faces intersected by a given H3 index.

Syntax

h3GetFaces(index)

Parameter

• index — Hexagon index number. UInt64.

Returned values

• Array containing icosahedron faces intersected by a given H3 index. Array(UInt64).

Example

Query:

SELECT h3GetFaces(599686042433355775) AS faces;

Result:

┌─faces─┐│ [7]   │└───────┘

## h3CellAreaM2​

Returns the exact area of a specific cell in square meters corresponding to the given input H3 index.

Syntax

h3CellAreaM2(index)

Parameter

• index — Hexagon index number. UInt64.

Returned value

• Cell area in square meters. Float64.

Example

Query:

SELECT h3CellAreaM2(579205133326352383) AS area;

Result:

┌───────────────area─┐│ 4106166334463.9233 │└────────────────────┘

Returns the exact area of a specific cell in square radians corresponding to the given input H3 index.

Syntax

h3CellAreaRads2(index)

Parameter

• index — Hexagon index number. UInt64.

Returned value

• Cell area in square radians. Float64.

Example

Query:

SELECT h3CellAreaRads2(579205133326352383) AS area;

Result:

┌────────────────area─┐│ 0.10116268528089567 │└─────────────────────┘

## h3ToCenterChild​

Returns the center child (finer) H3 index contained by given H3 at the given resolution.

Syntax

h3ToCenterChild(index, resolution)

Parameter

• index — Hexagon index number. UInt64.
• resolution — Index resolution. Range: [0, 15]. UInt8.

Returned values

• H3 index of the center child contained by given H3 at the given resolution. UInt64.

Example

Query:

SELECT h3ToCenterChild(577023702256844799,1) AS centerToChild;

Result:

┌──────centerToChild─┐│ 581496515558637567 │└────────────────────┘

## h3ExactEdgeLengthM​

Returns the exact edge length of the unidirectional edge represented by the input h3 index in meters.

Syntax

h3ExactEdgeLengthM(index)

Parameter

• index — Hexagon index number. UInt64.

Returned value

• Exact edge length in meters. Float64.

Example

Query:

SELECT h3ExactEdgeLengthM(1310277011704381439) AS exactEdgeLengthM;;

Result:

┌───exactEdgeLengthM─┐│ 195449.63163407316 │└────────────────────┘

## h3ExactEdgeLengthKm​

Returns the exact edge length of the unidirectional edge represented by the input h3 index in kilometers.

Syntax

h3ExactEdgeLengthKm(index)

Parameter

• index — Hexagon index number. UInt64.

Returned value

• Exact edge length in kilometers. Float64.

Example

Query:

SELECT h3ExactEdgeLengthKm(1310277011704381439) AS exactEdgeLengthKm;;

Result:

┌──exactEdgeLengthKm─┐│ 195.44963163407317 │└────────────────────┘

Returns the exact edge length of the unidirectional edge represented by the input h3 index in radians.

Syntax

h3ExactEdgeLengthRads(index)

Parameter

• index — Hexagon index number. UInt64.

Returned value

• Exact edge length in radians. Float64.

Example

Query:

SELECT h3ExactEdgeLengthRads(1310277011704381439) AS exactEdgeLengthRads;;

Result:

┌──exactEdgeLengthRads─┐│ 0.030677980118976447 │└──────────────────────┘

## h3NumHexagons​

Returns the number of unique H3 indices at the given resolution.

Syntax

h3NumHexagons(resolution)

Parameter

• resolution — Index resolution. Range: [0, 15]. UInt8.

Returned value

• Number of H3 indices. Int64.

Example

Query:

SELECT h3NumHexagons(3) AS numHexagons;

Result:

┌─numHexagons─┐│       41162 │└─────────────┘

## h3PointDistM​

Returns the "great circle" or "haversine" distance between pairs of GeoCoord points (latitude/longitude) pairs in meters.

Syntax

h3PointDistM(lat1, lon1, lat2, lon2)

Arguments

• lat1, lon1 — Latitude and Longitude of point1 in degrees. Float64.
• lat2, lon2 — Latitude and Longitude of point2 in degrees. Float64.

Returned values

• Haversine or great circle distance in meters.Float64.

Example

Query:

select h3PointDistM(-10.0 ,0.0, 10.0, 0.0) as h3PointDistM;

Result:

┌──────h3PointDistM─┐│ 2223901.039504589 │└───────────────────┘

## h3PointDistKm​

Returns the "great circle" or "haversine" distance between pairs of GeoCoord points (latitude/longitude) pairs in kilometers.

Syntax

h3PointDistKm(lat1, lon1, lat2, lon2)

Arguments

• lat1, lon1 — Latitude and Longitude of point1 in degrees. Float64.
• lat2, lon2 — Latitude and Longitude of point2 in degrees. Float64.

Returned values

• Haversine or great circle distance in kilometers. Float64.

Example

Query:

select h3PointDistKm(-10.0 ,0.0, 10.0, 0.0) as h3PointDistKm;

Result:

┌─────h3PointDistKm─┐│ 2223.901039504589 │└───────────────────┘

Returns the "great circle" or "haversine" distance between pairs of GeoCoord points (latitude/longitude) pairs in radians.

Syntax

h3PointDistRads(lat1, lon1, lat2, lon2)

Arguments

• lat1, lon1 — Latitude and Longitude of point1 in degrees. Float64.
• lat2, lon2 — Latitude and Longitude of point2 in degrees. Float64.

Returned values

• Haversine or great circle distance in radians. Float64.

Example

Query:

select h3PointDistRads(-10.0 ,0.0, 10.0, 0.0) as h3PointDistRads;

Result:

┌────h3PointDistRads─┐│ 0.3490658503988659 │└────────────────────┘

## h3GetRes0Indexes​

Returns an array of all the resolution 0 H3 indexes.

Syntax

h3GetRes0Indexes()

Returned values

• Array of all the resolution 0 H3 indexes. Array(UInt64).

Example

Query:

select h3GetRes0Indexes as indexes ;

Result:

┌─indexes─────────────────────────────────────┐│ [576495936675512319,576531121047601151,....]│└─────────────────────────────────────────────┘

## h3GetPentagonIndexes​

Returns all the pentagon H3 indexes at the specified resolution.

Syntax

h3GetPentagonIndexes(resolution)

Parameter

• resolution — Index resolution. Range: [0, 15]. UInt8.

Returned value

Example

Query:

SELECT h3GetPentagonIndexes(3) AS indexes;

Result:

┌─indexes────────────────────────────────────────────────────────┐│ [590112357393367039,590464201114255359,590816044835143679,...] │└────────────────────────────────────────────────────────────────┘

## h3Line​

Returns the line of indices between the two indices that are provided.

Syntax

h3Line(start,end)

Parameter

• start — Hexagon index number that represents a starting point. UInt64.
• end — Hexagon index number that represents an ending point. UInt64.

Returned value

Array of h3 indexes representing the line of indices between the two provided indices. Array(UInt64).

Example

Query:

 SELECT h3Line(590080540275638271,590103561300344831) as indexes;

Result:

┌─indexes────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐│ [590080540275638271,590080471556161535,590080883873021951,590106516237844479,590104385934065663,590103630019821567,590103561300344831] │└────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘

## h3Distance​

Returns the distance in grid cells between the two indices that are provided.

Syntax

h3Distance(start,end)

Parameter

• start — Hexagon index number that represents a starting point. UInt64.
• end — Hexagon index number that represents an ending point. UInt64.

Returned value

• Number of grid cells. Int64.

Returns a negative number if finding the distance fails.

Example

Query:

 SELECT h3Distance(590080540275638271,590103561300344831) as distance;

Result:

┌─distance─┐│        7 │└──────────┘

## h3HexRing​

Returns the indexes of the hexagonal ring centered at the provided origin h3Index and length k.

Returns 0 if no pentagonal distortion was encountered.

Syntax

h3HexRing(index, k)

Parameter

• index — Hexagon index number that represents the origin. UInt64.
• k — Distance. UInt64.

Returned values

Example

Query:

 SELECT h3HexRing(590080540275638271, toUInt16(1)) AS hexRing;

Result:

┌─hexRing─────────────────────────────────────────────────────────────────────────────────────────────────────────────┐│ [590080815153545215,590080471556161535,590080677714591743,590077585338138623,590077447899185151,590079509483487231] │└─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘

## h3GetUnidirectionalEdge​

Returns a unidirectional edge H3 index based on the provided origin and destination and returns 0 on error.

Syntax

h3GetUnidirectionalEdge(originIndex, destinationIndex)

Parameter

• originIndex — Origin Hexagon index number. UInt64.
• destinationIndex — Destination Hexagon index number. UInt64.

Returned value

• Unidirectional Edge Hexagon Index number. UInt64.

Example

Query:

 SELECT h3GetUnidirectionalEdge(599686042433355775, 599686043507097599) as edge;

Result:

┌────────────────edge─┐│ 1248204388774707199 │└─────────────────────┘

## h3UnidirectionalEdgeIsValid​

Determines if the provided H3Index is a valid unidirectional edge index. Returns 1 if it's a unidirectional edge and 0 otherwise.

Syntax

h3UnidirectionalEdgeisValid(index)

Parameter

• index — Hexagon index number. UInt64.

Returned value

• 1 — The H3 index is a valid unidirectional edge. UInt8.
• 0 — The H3 index is not a valid unidirectional edge. UInt8.

Example

Query:

 SELECT h3UnidirectionalEdgeIsValid(1248204388774707199) as validOrNot;

Result:

┌─validOrNot─┐│          1 │└────────────┘

## h3GetOriginIndexFromUnidirectionalEdge​

Returns the origin hexagon index from the unidirectional edge H3Index.

Syntax

h3GetOriginIndexFromUnidirectionalEdge(edge)

Parameter

• edge — Hexagon index number that represents a unidirectional edge. UInt64.

Returned value

• Origin Hexagon Index number. UInt64.

Example

Query:

 SELECT h3GetOriginIndexFromUnidirectionalEdge(1248204388774707197) as origin;

Result:

┌─────────────origin─┐│ 599686042433355773 │└────────────────────┘

## h3GetDestinationIndexFromUnidirectionalEdge​

Returns the destination hexagon index from the unidirectional edge H3Index.

Syntax

h3GetDestinationIndexFromUnidirectionalEdge(edge)

Parameter

• edge — Hexagon index number that represents a unidirectional edge. UInt64.

Returned value

• Destination Hexagon Index number. UInt64.

Example

Query:

 SELECT h3GetDestinationIndexFromUnidirectionalEdge(1248204388774707197) as destination;

Result:

┌────────destination─┐│ 599686043507097597 │└────────────────────┘

## h3GetIndexesFromUnidirectionalEdge​

Returns the origin and destination hexagon indexes from the given unidirectional edge H3Index.

Syntax

h3GetIndexesFromUnidirectionalEdge(edge)

Parameter

• edge — Hexagon index number that represents a unidirectional edge. UInt64.

Returned value

A tuple consisting of two values tuple(origin,destination):

• origin — Origin Hexagon index number. UInt64.
• destination — Destination Hexagon index number. UInt64.

Returns (0,0) if the provided input is not valid.

Example

Query:

 SELECT h3GetIndexesFromUnidirectionalEdge(1248204388774707199) as indexes;

Result:

┌─indexes─────────────────────────────────┐│ (599686042433355775,599686043507097599) │└─────────────────────────────────────────┘

## h3GetUnidirectionalEdgesFromHexagon​

Provides all of the unidirectional edges from the provided H3Index.

Syntax

h3GetUnidirectionalEdgesFromHexagon(index)

Parameter

• index — Hexagon index number that represents a unidirectional edge. UInt64.

Returned value

Array of h3 indexes representing each unidirectional edge. Array(UInt64).

Example

Query:

 SELECT h3GetUnidirectionalEdgesFromHexagon(1248204388774707199) as edges;

Result:

┌─edges─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐│ [1248204388774707199,1320261982812635135,1392319576850563071,1464377170888491007,1536434764926418943,1608492358964346879] │└───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┘

## h3GetUnidirectionalEdgeBoundary​

Returns the coordinates defining the unidirectional edge.

Syntax

h3GetUnidirectionalEdgeBoundary(index)

Parameter

• index — Hexagon index number that represents a unidirectional edge. UInt64.

Returned value

Example

Query:

 SELECT h3GetUnidirectionalEdgeBoundary(1248204388774707199) as boundary;

Result:

┌─boundary────────────────────────────────────────────────────────────────────────┐│ [(37.42012867767779,-122.03773496427027),(37.33755608435299,-122.090428929044)] │└─────────────────────────────────────────────────────────────────────────────────┘